The newest epidemiological evidence suggest that UVA as well as UVB is associated with human melanoma

Epidemiological studies published over the last years demonstrated the association between sunbed use and melanoma.

Many countries restrict the amount of UVB (vitamin D) from tanning beds (due to mouse study)

UVB decreases faster than UVA when far from equator or winter season

Confusion/Disagreement

Sunburn (Erythema), cataracts, and development of skin cancer are related mostly to UVB radiation.
Ban all people under age 18 from using tanning beds
Increase alcohol consumption is strongly associated with increased melanoma (see bottom of page)

Current sunscreen controversies: a critical review.

Background/purpose: Sunscreens are believed to be a valuable tool in providing photoprotection against the detrimental effects of UV radiation, a known carcinogen. However, a number of controversies have developed regarding their safety and efficacy. This review summarizes the relevant studies surrounding these controversies.

Methods: Evidence of the prevention of skin cancer, an oft-cited reason for sunscreen use, was examined as it pertains to squamous cell carcinoma, basal cell carcinoma and melanoma. We also reviewed studies examining the effects of sunscreen on the synthesis of vitamin D, an essential nutrient whose role in health and disease continues to grow. Lastly, we analyzed studies surrounding the safety and toxicity of oxybenzone, retinyl palmitate and nanoparticles of zinc oxide (ZnO) and titanium dioxide (TiO(2) ).

Results: The overwhelming majority of available data is drawn from studies conducted using antiquated sunscreen formulations.
Nonetheless, our research revealed that topical use of sunscreen protects against squamous cell carcinoma, does not cause vitamin D deficiency/insufficiency in practice and has not been demonstrated to adversely affect the health of humans.

Comment in a NYT interview of Dr. Bernard Ackerman, Demratoligist, who has authored 600 papers
"the field is just replete with nonsense." For example, Dr. Ackerman does not believe that the link between melanoma and sun exposure (a central dogma of dermatology) has been proven.
He is deeply tanned and is not afraid to expose his body to the sun. Dr. Ackerman does, however, recommend that folks avoid excessive skin exposure to avoid premature aging of the skin.
He also does not believe that sunburn, even the kind that causes blistering of the skin, necessarily leads to cancer later in life.
Basically, according to Dr. Ackerman, "the research is inconsistent and fails to make the case."

Sunlight Instutiute refutes the claim that melanoma is caused by sunlight

If already have had skin cancer, a form of Vitamin B3 lowers the rate of future ones by 23% - RCT May 2015

Common vitamin reduces recurrence of some skin cancers Washington Post
Year-long study in Australia using 500 milligrams of nicotinamide twice a day
Vitamin B3 provides skin cells with a boost of energy and intensifies the rate of skin repair.
"It's safe, it's almost obscenely inexpensive and it's widely available,"
People who haven't been diagnosed with such cancers should not take nicotinamide preventively, she said.
Results will be presented in late May 2015 at American Society of Clinical Oncology conference in Chicago